1. Technical Field of the Invention
The present invention relates to a scroll compressor mainly used in professional or commercial and household freezing and air-conditioning systems.
2. Prior Art
In a motor-driven compressor for freezing and air-conditioning, the compression unit is either a reciprocating type or a rotary type of unit. Both types of units are used in the field of freezing and air-conditioning in household and professional or commercial system. At the present time, both types of compressors are growing in use due to their affordable cost and excellent performance. In particular, a scroll type compressor unit is being employed because such a unit is highly efficient, has low noise, and has low vibration.
The scroll compression mechanism used in the scroll compressor, as is well known, includes a fixed scroll and an orbiting scroll, each having vortex blades that are engaged with each other, with several compression chambers formed between them. Each compression chamber compresses a refrigerant by decreasing in volume as the refrigerant the moves from an outer circumferential side in fluid communication with a suction port to an inner circumference side in communication with a discharge port, by an orbiting motion of the orbiting scroll. The compressed refrigerant is discharged from the discharge port.
In order for the orbiting scroll to move in a proper manner to compress the refrigerant, the orbiting scroll is supported by an Oldham ring, which is used to provide an orbiting motion for the orbiting scroll without rotating the orbiting scroll. The Oldham ring is supported by a fixing member that allows the Oldham ring to move.
The Oldham ring slides between the fixing member and orbiting scroll. The orbiting scroll, fixed scroll, fixing member, and Oldham ring are all made of ferriferous materials.
As the refrigerant, specific CFC (chloro-fluoro-carbon) R12 or designate HCFC (Hydro-chloro-fluoro-carbon) R22 has been used. As compared with the refrigerants used in the past, such as sulfur dioxide and methyl chloride, specific CFC is stable chemically, free from toxicity, and has been widely used as an ideal refrigerant for a long period.
Lately, it is disclosed that chlorine atoms, contained in the molecule of specific CFC, destroy the ozone layer. As a result, substitute refrigerants are being developed and used. As practical substitute refrigerants, chlorine-free HFC (Hydro-fluoro-carbon) and similar refrigerants have been proposed (Hydraulic and Pneumatic Technology, June 1994, published by Nippon Kogyo Shuppan).
However, a compressor using such a substitute refrigerant is not expected to have as excellent lubricity as when using the conventional specific CFC. In particular, the substitute refrigerant does not contain chlorine, which acts as a lubricant. Accordingly, the sliding condition is severe, and in the support structure using an Oldham ring for the orbiting scroll as in the prior art, the sliding parts are likely to wear out, shortening the life of the support structure. This is because the substitute refrigerant cannot be expected to lubricate the Oldham ring of the support structure and the sliding parts of the orbiting scroll and fixing member. The oil film is partly cut and a boundary lubrication state tends to occur. As a result, in this boundary lubrication state portion, which forms with the materials being ferriferous, leads to adhesion of the support structure and a shortened life for this structure.
The shortening of the life of the support structure is a particularly serious problem and is fatal in practical use, especially in a maintenance-free compressor operated for a long period. In an enclosed type of compressor, the life of the support structure itself is supposed to equal the life of the entire compressor.
Hence, it is a primary object of the present invention to solve the above problems, and disclose a scroll compressor free from the problems of having a shortened life due to the wearing of the support structure when using chlorine-free substitute refrigerant.